Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$66.54	5.530%	$70.2197	$70.22	$70.20	$70.20
Purchase #2	$236.98	5.712%	$250.5163	$250.52	$250.50	$250.50
Purchase #3	$44.80	4.608%	$46.8644	$46.86	$46.85	$46.90
Purchase #4	$78.44	13.554%	$89.0718	$89.07	$89.05	$89.10
Purchase #5	$77.62	5.863%	$82.1709	$82.17	$82.15	$82.20
Purchase #6	$211.39	5.364%	$222.729	$222.73	$222.75	$222.70
Purchase #7	$28.53	12.639%	$32.1359	$32.14	$32.15	$32.10
7 purchase totals =	$744.30		$793.7080	$793.71	$793.65	$793.70